Intramedullary prostheses



P. WITTEBOL May 23, 1967 INTRAMEDULLARY PROSTHESES Filed Dec. '7, 1964 FIG. 2

FIG. 1

INVENTOR Poul Winebol I W I I ATTO NEYS United States Patent Office 3,320,951 Patented May 23, 1967 3,320,951 INTRAMEDULLARY PROSTHESES Paul Wittebol, Dijsselhofplantsoen 4, Amsterdam, Netherlands Filed Dec. 7, 1964, Ser. No. 416,282 Claims priority, application Great Britain, Apr. 21, 1964, 16,504/ 64 Claims. (Cl. 128-92) The present invention relates to intramedullary prostheses for the hip joint. The metal intramedullary prosthesis has gained a firm footing in the surgery of the hip joint.

The results obtained with prostheses of the Moore type may on the whole be regarded as very favorable. Those prostheses, however, were only used in cases of recent fracture of the femoral neck in patients of advanced age and sometimes also in younger patients in whom an earlier treatment, aimed at consolidation of the fracture of the neck had failed and had resulted either in pseudarthrosis or in necrosis of the femoral head.

The indications therefore were rather limited, but it soon appeared that there was a distinct ditference between the results in cases where the recent fracture had been treated with a prosthesis and those in which the prosthesis was only applied later on. In the latter group, the results were less favorable than in the former. Nor is this surprising. Owing to the protracted inactivity and the deformation of the hip joint during the period preceding the application of the prosthesis, the risk of posttraumatic arthrosis is much greater and the shortening and induration of the soft parts surrounding the joint undoubtedly also contribute to the delay of the rehabilitation process.

Another factor was that the patients in whom the prostheses were applied secondarily, were on the average 68 years old, so that on the whole heavier demands were made of the joint.

This distinct difference in results means that caution is indicated in connection with the application of known prostheses for the femoral head and neck.

In elderly persons in whom the joint is not often used for weight-bearing, the imperfections of these known prostheses may not become apparent. In younger subects, on the other hand, in whom one may expect a heavier and more protracted stress on the point, some failures will be unavoidable.

Experience with prostheses of the Moore type has made surgeons and other familiar wit-h its deficiencies.

While the Moore prosthesis has a wide, flat stem and can be firmly fixed in the femoral shaft, it is impossible with the Moore prosthesis to restore the correct angle of anteversion. It has been found that it is impossible even by correct preparation of the medullary cavity, to place the Moore or other known types of femoral prostheses in the anteversion position desired by the surgeon. The medullary cavity at the level of the lesser trochanter, where the prosthesis finds most of its support, is fiat anteriorly, in a frontal plane. It is impossible to give this cavity a different direction without sacrificing part of the cortical layer of the bone at this site.

It is possible, on the other hand, to widen the medullary cavity of the proximal femur by fraising to such an extent that the stem of the prosthesis could be placed obliquely in it, obliquely, that is, in reference to the anterior surface of the femur. However, this would cause the prosthesis to lose its indispensable stability, and rotation would then always occur in a posterior direction i.e. in the sense of retroversion, which would favor and cause luxation of the prosthesis.

The loss of anteversion after prosthetic replacement of the femoral head is a more serious objection than many surgeons feel inclined to admit. Walking with the leg in exorotation, rapid fatigue, pain in the musculature of the hip and disorders of the knee are largely brought about by the absence of the normal anteversion. A tacit admission of the impossibility of applying the prosthesis at the correct angle of anteversion lies in the fact that a known prosthesis is often used in combination with an artificial resin that is still plastic. The proximal femur is scooped out to such a degree that the prosthesis can be inserted in the desired position, and the remaining space is then filled with the plastic mass that is left to harden in the body.

In itself, the attempt to accomplish an optimal position of the prosthesis is praiseworthy. However, the experiences with the acrylic prosthesis in the still recent past (1952-1956) have not been of such a kind that failures are excluded. Non-polymerized remnants of the monomer, which is highly toxic, may very well have caused the enormous destruction of bone that has been observed in cases treated with the old acrylic prosthesis.

When, after the use of plastic material for the application of the prosthesis, the whole of the proximal femur is destroyed in a similar way, reconstruction becomes very difficult indeed.

In order to overcome the disadvantages described above in a practical and simple way, the metal intramedullary prosthesis according to the present invention is provided with a globular head, a stem having an extended shape, and a connecting portion between the globular head and the stem of such a length that the center of the globular head is positioned in the center of the natural hip joint. In this structure, according to the invention, the center of said globular head lies in a plane that encloses an angle with the longitudinal medial plane of the flat extended stern, whereby the supporting face at the upper end of the stem is positioned perpendicularly to said plane through said head.

A flat, long stem guarantees optimum resistance to rotation. A supporting plane between the prosthesis and the residual neck of the femur approximately perpendicular to the direction of the pressure, greatly reduces the tendency to shifting and tilting and thereby again increases the stability of the prosthesis as a whole. On the basis of these features a prosthesis is provided which offers the possibility of anatomical normalization.

The improved prosthesis has a stem longer and heavier than known prostheses. Since a complete normalization of the height is practically never obtained with prostheses of the Moore type, the neck of the prosthesis according to the present invention has been lengthened and, importantly, the neck is connected to the stem at an angle.

In order that the invention may be more clearly understood, reference will now be made to the accompanying drawings which show one embodiment thereof by way of example.

In the drawings:

FIG. 1 is a front elevational view of an intramedullary prosthesis according to the present invention, and

FIG. 2 is a side elevational view of the prosthesis of FIG. 1.

Referring to the drawings, FIGS. 1 and 2., illustrating a prosthesis constructed according to the present invention, includes a stem 4, a neck 5, a head 6 and a supporting surface or plane 7 located at the upper end of the stem 4, between it and the neck 5.

The stem 4, as shown in FIG. 2, has an extended width throughout its length so as to provide optimum resistance to rotation in the femoral shaft. The neck 5, as shown in both FIGS. 1 and 2, extends upwardly with respect to the stem 4 and the surface 7 so as to provide substantially complete normalization of the height of the patient, which result has never been achieved with known prostheses.

Furthermore, this result is favored by the fact that the globular head 6 is connected at an angle to the stem 4 through the neck 5. This angle is apparent from the relationship shown in FIG. 1 between the stem 4 and the head 6 and the showing of the support surface 7 in FIG. 2, which engages the residual neck of the femur (not shown) and is substantially perpendicular to the direction of the pressure applied to the prosthesis. These relationships greatly reduce the tendency to shifting and tilting and increase the stability of the prosthesis as a whole.

When the prosthesis of the present invention is used to replace the head and neck portion of .a femur with a fractured neck, the postoperative normalization of the function of the hip joint is rapid because the patients movements with the substituted prosthesis are natural. There is no tendency to exorotation which often occurs with previously known types of prostheses.

While FIGS. 1 and 2 are referred to respectively as front and side views, it is apparent that a line through the upper portion of the stem 4, neck and head 6 extends inwardly, upwardly and forwardly with respect to the upper portion of the femur, and that the illustrated prosthesis is particularly constructed and arranged for the right femur.

In practice an anteversion angle of 13-15 produces the best result.

I claim:

1. A metal intramedullary prosthesis for a fracture of the femoral neck in the hip joint, comprising a widelyextending, upright, flat stem and a prosthetic globular head connected thereto by a neck portion having a supporting face at the upper end of the stem, said supporting face being positioned substantially perpendicularly to the direction of pressure to be applied by it during use, the center of the globular head being positioned outside the longitudinal axis of the stem, the connecting neck portion between the head and the stern having such a length that the center of the globular head lies in a plane perpendicular to said supporting face at the upper end of the stern that encloses an angle with the longitudinal medial plane of the flat stem.

2. A metal intr-amedullary prosthesis for a fracture of the femoral neck in the hip joint to be substituted for the head and adjacent neck portion of the femur, comprising a wide, upright, flat stem and a prosthetic globular head connected thereto by a neck portion having a supporting face at the upper end of the stern, said supporting surface being positioned substantially perpendicularly to the direction of pressure to be applied by it during use, the center of the globular head being located outside the longitudinal axis of the stem, the globular head extending from the neck to a position that a plane through the neck portion and the center of the globular head encloses an angle with a longitudinal medial plane extending edgewise through the flat stem. 7 3. A metal intramedullary prosthesis for a fracture of the femoral neck in the hip joint, comprising a wide, flat, upright stern and a prosthetic globular head connected thereto by a neck portion having a supporting surface at the upper end of the stem, said supporting surface being positioned substantially perpendicularly to the direction of pressure from the globular head, the center of the globular head being positioned outside of a longitudinal medial plane extending ed gewise through the flat stern, and the connecting neck portion between the head and the stern extending upwardly, inwardly and forwardly with respect to the upper portion of the stem.

4. A prosthesis as claimed in claim 3, in which the center of the globular head is located anteriorly of said plane extending edgewise through the stem.

5. A prothesis as claimed in claim 3, in which the Wide, flat sides of the stem face respectively anteriorly and posteriorly, and the center of the globular head is located anteriorly relative to the upper portion of the stern.

Austenal Laboratories ad of Moore Type Hip Prothesis in The Journal of Bone and Joint Surgery for January 1962 page 4.

RICHARD A. GAUDET, Primary Examiner.

J. W. HINEY, Assistant Examiner. 

1. A METAL INTRAMEDULLARY PROSTHESIS FOR A FRACTURE OF THE FEMORAL NECK IN THE HIP JOINT, COMPRISING A WIDELYEXTENDING, UPRIGHT, FLAT STEM AND A PROSTHETIC GLOBULAR HEAD CONNECTED THERETO BY A NECK PORTION HAVING A SUPPORTING FACE AT THE UPPER END OF THE STEM, SAID SUPPORTING FACE BEING POSITIONED SUBSTANTIALLY PERPENDICULARLY TO THE DIRECTION OF PRESSURE TO BE APPLIED BY IT DURING USE, THE CENTER OF THE GLOBULAR HEAD BEING POSITIONED OUTSIDE THE LONGITUDINAL AXIS OF THE STEM, THE CONNECTING NECK PORTION BETWEEN THE HEAD AND THE STEM HAVING SUCH A LENGTH THAT THE CENTER OF THE GLOBULAR HEAD LIES IN A PLANE PERPENDICULAR TO SAID SUPPORTING FACE AT THE UPPER END OF THE STEM THAT ENCLOSES AN ANGLE WITH THE LONGITUDINAL MEDIAL PLANE OF THE FLAT STEM. 